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    Re: Captain Cook & celestial navigation
    From: Robin Stuart
    Date: 2020 Jan 30, 13:07 -0800

    Frank you wrote:

    "...do you really count Maskelyne as a "great man"? It seems we're in the midst of a reactionary phase."

    As we will probably disagree on the precise threshold someone must rise above to qualify as a "great man" I suggest we let Maskelyne's accomplishments speak for themselves.

    Whatever category you place him in he does not deserve the now widespread myth that disparages his character and place in history. This myth was widely popularized by the publication of Dava Sobel's Longitude but appears to have its origins in the early 20th century in histories that were written by those firmly in the horological camp. I recommend Maskelyne: Astronomer Royal edited by Rebekah Higgitt for an explanation as to the origins and for an in-depth description of Maskelyne's life and achievements. Also as pointed out by Marcelo S a more balanced article can be found here.

    Maskelyne has been variously accused of greed for wanting the Longitude Prize for himself (although as Astronomer Royal he was not eligible to receive any) and personal anamosity toward John Harrison (although he recommended Harrison's son, William, for election to the Royal Society even though they were in the midst of effectively accusing him of corruption.)

    The statement in the Sky & Telescope "...his bias for using lunar distances delayed the acceptance of John Harrison’s H4 chronometer as the best method for determining longitude at sea" falls apart when when subjected to straightforward logical scrutiny.

    Comparing lunars to chronometers as a means of finding GMT the choice is obvious

    1) Chronometer: Read GMT off the dial

    2) Lunar Distance: Weather permitting and when the Moon is "in distance" have (ideally) three skilled observers simultaneously measure the lunar distance and altitudes of Moon and other body. Then sit down with your copy of the Nautical Alamanac and log tables, do some calculations and get GMT.

    According to the statement in the S&T article it was Maskelyne's bias that prevented him from seeing the obvious conclusion that option 1) is the best method for finding longitude at sea. There is a caveat however. You need to have a reliable marine chronometer (If I had eggs, I'd have ham and eggs...if I had ham!).

    Maybe Maskelyne was skeptical that a marine chronometer with the required characteristics could be produced but in that he was in good company. Isaac Newton pointed out "a good watch may serve to keep a reckoning at sea for some days and to know the time of a celestial observation; and for this end a good Jewel may suffice till a better sort of watch can be found out. But when longitude at sea is lost, it cannot be found again by any watch".

    It seems not unreasonable that the Commissioners of Longitude would want to make mighty sure that they had a workable solution to the problem of finding longitude that could be rolled out across his His Majesty's fleet before they emptied the coffers. Lunars could clearly be made available to all ships quite quickly and cheaply. The "delay" mentioned in the S&T statement probably refers to the requirement that Harrison should show how his chornometer could replicated before he received the final £10,000 installment of the prize. Put yourself in the Commisioners' shoes trying to explain to the First Sea Lord that the prize had been paid out and you had one just instance of a working chronometer but you don't know how it works or how to make any more. "Well, your Lordship, until it breaks down one of your ships will be able to find longitude!"

    I suspect that, from reading the popular accounts, many people would conclude that the advent of Harrison's chronometers was a "slam dunk" and that the misguided lunar distance method vanished off the face of the Earth. Of course Navlisters understand that lunars persisted for a long time afterwards. Chronometers were initially rare, expensive and delicate beasts that demanded considerable effort be devoted to their care and feeding. Great tomes were written on this subject (Shadwell, C.F.A. (1861). Notes on the Management of Chronometers and the Measurement of Meridian Distances. J. D. Potter, London. https://hdl.handle.net/2027/hvd.hn2vz5).  Shackleton's 1914 Imperial Trans-Antarctic Expedition set out with 24 chronometers onboard. Although rarely if ever used by that time the USNO continued to publish tables of lunar distances in the American Nautical Almanac until 1911. Maskelyne's influence and bias must have been far reaching indeed!

    If we are are in a reactionary phase then it is long overdue. Maybe it is time for the pendulum to swing completely in the other direction. After all he was the first to set up geographically distributed computer network (the computers were human and used to calculate and cross-check the NA) so perhaps he should be hailed as the father of the internet!

    Robin Stuart

       
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